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United States Patent | 6,228,900 |
Shen ,   et al. | May 8, 2001 |
The present invention discloses methods for enhancing the wear-resistance of polymers, the resulting polymers, and in vivo implants made from such polymers. One aspect of this invention presents a method whereby a polymer is irradiated, preferably with gamma radiation, then thermally treated, such as by remelting of annealing. The resulting polymeric composition preferably has its most oxidized surface layer removed. Another aspect of the invention presents a general method for optimizing the wear resistance and desirable physical and/or chemical properties of a polymer by crosslinking and thermally treating it. The resulting polymeric compositions is wear-resistant and may be fabricated into an in vivo implant.
Inventors: | Shen; Fu-Wen (Walnut, CA); McKellop; Harry A. (Los Angeles, CA); Salovey; Ronald (Rancho Palos Verdes, CA) |
Assignee: | The Orthopaedic Hospital and University of Southern California (Los Angeles, CA) |
Appl. No.: | 214586 |
Filed: | January 6, 1999 |
PCT Filed: | July 8, 1997 |
PCT NO: | PCT/US97/11947 |
371 Date: | June 8, 1999 |
102(e) Date: | June 8, 1999 |
PCT PUB.NO.: | WO98/01085 |
PCT PUB. Date: | January 15, 1998 |
Current U.S. Class: | 522/153; 522/154; 522/157; 522/161; 522/163; 522/164; 523/113; 523/115; 525/937; 526/351; 526/352 |
Intern'l Class: | A61F 002/00; A61F 002/32; C08J 003/28; C08F 110/02; C08F 110/06 |
Field of Search: | 522/163,164,161,153 523/113,115 525/937 526/351,352 623/18,19,20,21,22,23 |
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TABLE 1 3.3 Mrad Before remelting After remelting Distance peak melting degree of peak melting degree of from surface temperature crystallinity gel content temperature crystallinity gel content (mm) (.degree. C.) (%) (%) (.degree. C.) (%) (%) 34.8-35 135.3 59.6 91 131.4 52.5 94.7 35.8-36 135.4 60.2 91 131.5 51.2 94.7 36.8-37 135.3 60.5 91 131.4 51.9 94.7 37.8-38 135.3 60 91.1 131.3 52 95 (center)
TABLE 2 28 Mrad Before remelting After remelting Distance peak melting degree of peak melting degree of from surface temperature crystallinity gel content temperature crystallinity gel content (mm) (.degree. C.) (%) (%) (.degree. C.) (%) (%) 34.8-35 139.8 65.1 95.8 135 52 97.7 35.8-36 139.8 64.2 95.8 134.8 52.1 97.7 36.8-37 139.7 64.5 95.8 134.9 52.5 97.7 37.8-38 139.7 65.3 95.8 134.9 52.7 97.7 (center)
TABLE 3 Wear Rate Mean Wear (mm.sup.3 /million Rate .+-. Std Cup # Material cycles) Deviation N11 3.3 Mrad 20.8 21.1 .+-. 0.3 N16 Not 21.2 N17 remelted 21.4 R21 3.3 Mrad 17.7 18.6 .+-. 1.3 R26 Remelted 20.1 R27 18.0 N35 28 Mrad 0.29 0.25 .+-. 0.03 N31 Not 0.24 N32 remelted 0.24 R48 28 Mrad 0.36 0.36 .+-. 0.001 R45 Remelted 0.35 R49 0.36
TABLE 4 0-3 Million Cycles (non-aged) 3-7 Million Cycles Wear Rate Mean Wear Wear Rate Mean Wear (mm.sup.3 /million Rate .+-. Std (mm.sup.3 /million Rate .+-. Std Cup # Material cycles) Deviation Conditions cycles) Deviation N11 3.3 Mrad 20.8 21.1 .+-. 0.3 non-aged 21.2 -- N16 Not 21.2 aged 21.5 21.8 .+-. 0.5 N17 remelted 21.4 aged 22.2 R21 3.3 Mrad 17.7 18.6 .+-. 1.3 non-aged 17.5 -- R26 Remelted 20.1 aged 19.2 19.8 .+-. 1.0 R27 18.0 aged 20.5 N35 28 Mrad 0.29 0.25 .+-. 0.03 non-aged 0.03 -- N31 Not 0.24 aged -0.47 -0.71 .+-. 0.3 N32 remelted 0.24 aged -0.93 R48 28 Mrad 0.36 0.36 .+-. 0.001 non-aged 0.47 -- R45 Remelted 0.35 aged 0.08 -0.06 .+-. 0.2 R49 0.36 aged -0.20
TABLE 5 (1-5 million cycles) Wear Rate (mm.sup.3 / Mean Wear Rate .+-. SD Cup # Material million cycles) (mm.sup.3 /million cycles) N11 3.3 Mrad 20.46 20.12 .+-. 0.7* N16 Not 19.32 N17 remelted 20.59 R21 3.3 Mrad Remelted 17.04 17.51 .+-. 0.48* R26 18.0 R27 17.49 RA2 4.5 Mrad Remelted 9.93 9.28 .+-. 0.92 RA3 8.63 RB3 9.5 Mrad Remelted 2.39 2.22 .+-. 0.24 RB6 2.05 RC5 14.5 Mrad Remelted 1.26 1.17 .+-. 0.13 RC6 1.08 RD1 20.2 Mrad Remelted 0.26 0.12 .+-. 0.2 RD6 -0.02 RE3 24 Mrad Remelted -0.49 -0.59 .+-. 0.13 RE4 -0.68 RF2 50 Mrad Remelted -0.8 -- RG1 100 Mrad Remelted -6.88** -- *The wear data of the 3.3 Mrad materials in Example 2. **The wear rate in the period of 1-2 million cycles.
TABLE 6 Non-remelted Melting Remelted point Crystallinity Melting point Crystallinity Samples (.degree. C.) (%) (.degree. C.) (%) Non-irrad. 133.8 55 -- -- 3.3 Mrad 135.3 .+-. 0.1 60.1 .+-. 0.4 131.4 .+-. 0.1 51.8 .+-. 0.6 4.5 Mrad 136.2 .+-. 0.2 65.8 .+-. 1.6 131.6 .+-. 0.2 52.0 .+-. 1.3 9.5 Mrad 137.1 .+-. 0 67.1 .+-. 2.2 134.8 .+-. 0.2 53.3 .+-. 2.1 14.5 Mrad 137.5 .+-. 0.2 69.6 .+-. 1.6 135.0 .+-. 0.1 53.0 .+-. 1.5 20.2 Mrad 137.4 .+-. 0.1 70.8 .+-. 2.8 135.3 .+-. 0.1 52.1 .+-. 1.8 24 Mrad 137.9 .+-. 0.3 68.0 .+-. 1.3 135.2 .+-. 0.1 51.7 .+-. 1.2 50 Mrad 138.9 .+-. 0.2 67.0 .+-. 1.3 135.2 .+-. 0 52.8 .+-. 0.2 100 Mrad 140.2 .+-. 0.3 66.3 .+-. 2.7 130.8 .+-. 0.2 52.3 .+-. 1.7
TABLE 7 Non-remelted Remelted M.W. M.W. between Crosslink Gel between Crosslink Gel Degree of crosslinks density content Degree of crosslinks density content Samples swelling (g/mol) (mol %) (%) swelling (g/mol) (mol %) (%) 3.3 Mrad 5.29 8400 0.17 94.7 3.21 2500 0.56 98.1 4.5 Mrad 3.57 3500 0.40 97.8 3.15 2400 0.58 98.4 9.5 Mrad 2.82 1900 0.74 98.6 2.54 1400 1.0 98.9 14.5 Mrad 2.35 1100 1.27 98.7 2.36 1100 1.27 99.2 20.2 Mrad 2.27 1000 1.40 98.8 2.25 1000 1.40 99.2 24 Mrad 2.17 900 1.56 98.7 2.24 1000 1.40 99.2 50 Mrad 1.92 600 2.33 98.7 2.17 900 1.56 99.1 100 Mrad 1.71 400 3.50 98.6 1.71 400 3.50 98.5
TABLE 8 Tensile Strength at Tensile Strength at Elongation at Materials Yield (MPa) Break (MPa) Break (%) Non-irradiated 23.3 .+-. 0.11 52.1 .+-. 4.78 356 .+-. 23 Without remelting 4.5 Mrad 24.9 .+-. 0.33 46.9 .+-. 2.91 314 .+-. 12 9.5 Mrad 25.3 .+-. 0.12 47.6 .+-. 2.76 251 .+-. 8 14.5 Mrad 25.7 .+-. 0.25 46.4 .+-. 1.20 213 .+-. 5 20.2 Mrad 26.2 .+-. 0.27 40.2 .+-. 2.72 175 .+-. 7 24 Mrad 26.4 .+-. 0.23 40.0 .+-. 5.42 164 .+-. 17 After remelting 4.5 Mrad 21.5 .+-. 0.33 45.6 .+-. 8.89 309 .+-. 20 9.5 Mrad 21.3 .+-. 0.60 43.2 .+-. 2.80 252 .+-. 8 14.5 Mrad 21.8 .+-. 0.29 36.8 .+-. 1.72 206 .+-. 9 20.2 Mrad 21.9 .+-. 0.18 34.3 .+-. 3.61 185 .+-. 8 24 Mrad 21.7 .+-. 0.25 32.3 .+-. 2.81 160 .+-. 19